1. Field of the Invention
The present invention relates to a fuel tank for storing fuel.
2. Related Background Art
If there is a space above the fuel level in the fuel tank, the fuel will be evaporated and this evaporated fuel could be emitted to the atmosphere. For example, Japanese Laid-Open Patent Application No. H8-170568 discloses a fuel tank constructed in such structure that a fuel storage chamber for storing the fuel is made of an extensible envelope film and that the envelope film expands and contracts according to the amount of the fuel in the fuel storage chamber, thereby preventing the evaporated fuel from appearing above the fuel level in the fuel storage chamber. Specifically, the above envelope film is composed of an upper wall, a lower wall, and a side wall of a bellows shape connecting these upper wall and lower wall to each other, and the lower wall of the envelope film is attached to a flat bottom wall of a housing. The upper wall of the envelope film moves up and down in the housing, depending upon the fuel amount in the fuel storage chamber, and the side wall expands and contracts with the up and down motion of the upper wall. The capacity of the fuel storage chamber thus increases and decreases with the upper and down motion of the upper wall and the expansion and contraction of the side wall of the envelope film.
The inventor, however, found out the fact that, because in the above fuel tank the lower wall of the envelope film forming the fuel storage chamber was fixed to the bottom wall of the housing, the lower wall was not displaced or deformed according to the fuel amount in the fuel storage chamber and the maximum amount of the fuel that was able to be stored in the fuel storage chamber of the above fuel tank was thus smaller than the maximum that would have been expected if the lower wall should have been displaceable or deformable in the direction to increase the capacity of the fuel storage chamber, according to the fuel amount in the fuel storage chamber.
The present invention has been accomplished in order to solve the above issue and an object of the invention is to provide a fuel tank provided with a fuel storage chamber that is deformable according to the amount of fuel stored therein, wherein the amount of the fuel that can be stored in the fuel storage chamber is maintained at the maximum.
A fuel tank of the present invention is a fuel tank comprising a fuel storage chamber that is deformable according to the amount of fuel stored therein, wherein the fuel storage chamber comprises a lower wall to be curved downward according to increase in the amount of fuel and is supported by a support member that allows the lower wall to be curved downward.
Since this fuel tank of the present invention is constructed in such structure that the lower wall forming the fuel storage chamber becomes curved downward according to the increase in the amount of fuel and that at this time the support member for supporting the fuel storage chamber does not restrain the downward curvature of the lower wall, the capacity of the fuel storage chamber is increased as compared with the fuel tank not allowing such deformation of the lower wall.
Specifically, the fuel storage chamber is composed of an upper wall and a lower wall of a polygon opposed to each other, and peripheral walls connecting these upper wall and lower wall.
The walls constituting the fuel storage chamber are formed, specifically, in multilayered structure of resin.
The support member is preferably constructed in structure for supporting a peripheral part of the fuel storage chamber. When this structure is adopted, the support member for supporting the peripheral part of the fuel storage chamber does not restrain the downward curvature of the lower wall and, therefore, the lower wall is well curved downward.
The peripheral part of the fuel storage chamber is composed, specifically, of the peripheral walls, and connecting portions of the upper wall and lower wall connected to the peripheral walls.
The support member is preferably configured to support corners of the peripheral part. When this configuration is employed, the peripheral part, particularly at the corners, has higher rigidity than the other portions, because there are the upper wall, the lower wall, and vertical connecting portions for connecting adjacent peripheral walls. Hence the fuel storage chamber is supported well even by the structure for supporting only the corners. Since the support member is configured to support only the corners of the peripheral part as against the invention for supporting the whole of the peripheral part, the configuration of the support member is simplified. Even if the peripheral walls are deformed with deformation of the lower wall, the corners will rarely be deformed because of their high rigidity as described above. Therefore, the deformation of the peripheral walls and the lower wall is not restrained even in the structure for supporting the corners.
In a preferred configuration the peripheral walls have a flange member and the support member supports the flange member. When this configuration is employed, the support member supporting the flange member of the peripheral walls does not restrain the downward curvature of the lower wall and, therefore, the lower wall is well curved downward.
The support member is preferably configured to comprise vibration suppressing means for suppressing input of vibration from the outside of the fuel storage chamber thereinto. When this configuration is adopted, the vibration suppressing means suppresses vibration of the fuel storage chamber and also suppresses production of noise.
In a preferred configuration the vibration suppressing means is an elastic member and this elastic member supports the fuel storage chamber in a vibration-isolating manner. When this configuration is adopted, the vibration of the fuel storage chamber, for example, due to acceleration G or vertical G is transmitted to the elastic member and elastic action of this elastic member suppresses the vibration of the fuel storage chamber and also suppresses production of noise.
Here, the elastic member is, specifically, a vibration-isolating material of rubber.
Another specific example of the elastic member is a coil spring.
The support member is preferably an elastically deformable support member, which abuts against the lower wall, for supporting the lower wall, the elastically deformable support member being arranged to elastically deform while dispersing a load exerted by the lower wall according to the downward curvature of the lower wall. When this configuration is employed, the elastically deformable support member as the support member abuts against the lower wall and supports the lower wall with elastically deforming while dispersing the load exerted by the lower wall according to the downward curvature of the lower wall. Therefore, the support member allows the downward curvature of the lower wall while receiving the weight of the fuel storage chamber including the fuel. Thanks to this, the lower wall is well curved downward. Since the elastically deformable support member supports the fuel storage chamber while elastically deforming, it suppresses the vibration of the fuel storage chamber and also suppresses the production of noise.
Here, the elastically deformable support member is, specifically, a plurality of sheetlike resin members stretched so as to receive the lower wall.
Another specific example of the elastically deformable support member is a plurality of wirelike resin members stretched so as to receive the lower wall.
Another specific example of the elastically deformable support member is a foamed member on which the lower wall is mounted.
Another specific example of the elastically deformable support member is a spring member on which the lower wall is mounted.
Still another specific example of the elastically deformable support member is a rubber member on which the lower wall is mounted.
Here, for example, where the upper wall is arranged to be curved upward according to the increase in the fuel amount in order to further increase the amount of fuel to be stored in the fuel storage chamber, the fuel storage chamber is more curved downward than the upward curvature of the upper wall with increase of the fuel amount, because of the weight of the fuel storage chamber including the fuel. Therefore, deformation amounts of the upper wall and the lower wall are different from each other, which could result in twisting and in turn breaking the peripheral walls connecting them and making the capacity of the fuel storage chamber instable. Further, where a fuel meter (gage) for measuring the fuel amount of the fuel storage chamber is constructed to measure the fuel amount, for example, according to the deformation of the upper wall or the lower wall, the measurement will be inaccurate.
In contrast with it, the elastically deformable support member permits the downward curvature of the lower wall while receiving the weight of the fuel storage chamber including the fuel, as described above, so that the deformation amounts of the upper wall and the lower wall can be equalized. This prevents the breakage due to the twisting of the peripheral walls, stabilizes the capacity of the fuel storage chamber, and permits accurate measurement of the fuel amount.
When the support member is configured to have deformation amount adjusting means, which abuts against the lower wall, for adjusting a deformation amount of the downward curvature of the lower wall so as to match with a deformation amount of curvature of the upper wall, the deformation amounts of the upper wall and the lower wall become nearly equal to each other, which prevents the breakage due to the twisting of the peripheral walls, which stabilizes the capacity of the fuel storage chamber, and which permits the accurate measurement of the fuel amount.
In a preferred configuration there is provided curvature deformation regulating means for regulating the downward curvature of the lower wall at predetermined magnitude, below the fuel storage chamber. When this configuration is employed, the curvature deformation regulating means provided below the fuel storage chamber regulates the downward curvature of the lower wall at the predetermined magnitude, so that the lower wall is not deformed excessively over the predetermined magnitude. This protects the lower wall.
The curvature deformation regulating means is preferably an auxiliary fuel tank, located below the fuel storage chamber and connected to the fuel storage chamber, for temporarily storing the fuel from the fuel storage chamber. When this configuration is adopted, the auxiliary fuel tank is utilized as the curvature deformation regulating means and there is, therefore, no dead space below the fuel storage chamber. Therefore, this compactifies the fuel tank and, further, improves mountability of the whole fuel tank including the auxiliary fuel tank. In addition, the fuel in the fuel storage chamber is supplied to the auxiliary fuel tank with reliability, because the auxiliary fuel tank is located below the fuel storage chamber.
The auxiliary fuel tank is preferably configured in a shape to match with the shape of the lower wall during the downward curvature of the lower wall. When this configuration is employed, protection of the lower wall is further enhanced, because the shape of the auxiliary fuel tank matches with the shape of the lower wall during the downward curvature of the lower wall.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.